Tennis and baseball are seasonal activities. A tennis ball throwing machine and a baseball throwing machine may have many features and structural parts in common as well as features and parts unique with each activity. To have separate machines for each activity requires additional storage and greater investment than a single machine with quickly and easily converted attachments for adapting the machine for multiple uses.
A convertable baseball and tennis practice machine has a market in all baseball activities from Little League, up through high school, college and professional ranks. Additionally, private clubs and public parks with tennis courts have a use for such a machine. Commercial operators can now convert seasonally from one activity to the other and keep their commercial facilities open for longer seasonal periods. This, of course, enhances their profit potential.
In making a machine convertable many problems arise because of the basic differences between tennis balls and baseballs and between the various baseballs themselves and between the various tennis balls. The barrels must accommodate these differences and still eject the balls accurately and reliably. Also a feed mechanism must accommodate up to 200 tennis balls, without jamming or malfunctioning and feed any kind of baseball or tennis ball into the ejection barrel without operator assistance.
Whereas baseballs should be pitched accurately and consistently for batting practice, tennis balls should be hurled both accurately for beginners and randomly over a net to give the experienced player practice in specific shots and in following a ball as an opponent might return it. Also the velocity of the ball should vary.
Still another problem is in transporting the machine and moving it onto and off a tennis court or baseball batting area, making it quickly dismantable or assembled for use, and still have a machine that will stay stable when in use.